British World No 4 Andy Murray has been made the top seed for next week's LA Open after the late withdrawal of second-ranked Novak Djokovic.
Serbian Djokovic pulled out of the ATP Tour event late on Friday night, citing personal reasons, organisers said.
Czech Radek Stepanek, the 2007 champion, also withdrew on Friday due to a knee injury.
"It's certainly disappointing to lose players like Novak and Radek," tournament director Bob Kramer said in a statement.
"We were looking forward to Novak making his debut in LA, but we're very fortunate that Andy Murray, another top-five player, will be able to join us."
Murray, who has been given a wild card entry, will be making his first appearance at the event held at the LA Tennis Center.
Big-serving American Sam Querrey, who won last year's title, has been seeded second with Cypriot Marcos Baghdatis third and Spaniard Feliciano Lopez fourth.
